The present disclosure relates to the production of a polymer composite component with increased compaction, alignment, and degree of cure through the increase of chain mobility.
Organic compounds have been developed and used for a range of applications. Polymers, as a class of organic compounds, have been designed to be applied as monolithic materials or as matrices for composite structures reinforced with various types of fibers or particulates. There are two major forms of polymeric materials: thermoplastic and thermoset compounds.
Thermoplastic materials rely on organic molecules with a range of chain lengths and a range of pendent features from none to complex aromatics. These polymers are broadly classified by the ability to heat the material and form it into shapes. This can be accomplished by allowing discrete polymer chains to move about each other freely with the exception of physical tangles. These materials can be heated, shaped, and cooled repeatedly with no change in or loss of material properties. Thermoset compounds have the added complexity of cross-linking to a level where thermal energy input does not allow further mobility of the prior individual organic molecules. Once these compounds are formed, they cannot be re-heated and re-shaped as heating does not return the material to its original uncured state. These compounds are very stable relative to dimension, as crystallization cannot readily progress once the final cross-linked component is formed. Of the two main types of polymers, thermoset compounds are more capable of stability at very high temperatures and are relatively capable of resisting environmental attack.
As applications expand, there is a growing need to increase the effective operating temperature and environmental capabilities of organic polymeric materials. As polymeric materials are increased in temperature, they can degrade by breaking of bonds within the polymeric structure or by further reaction of the polymer with other chemical species, effectively changing the entire make-up and capability of the material. To increase the temperature and environmental capability of high performance polymeric materials, increased quantity and strength of inter-chain interactions, bonding, and cross-linking are desired. These interactions between chains can be of several types, including covalent cross-link bonds, ionic bonds and weaker Van der Waals forces from polar molecule sites.
Recent work has shown that simple polymeric materials, such as polyethylene can be processed by strain from extrusion or other mechanical deformation processes to align and bring long polymer chains into very orderly close proximity to facilitate formation of large numbers of Van der Waals forces. This results in greatly increased strength, strain to failure, and overall toughness of this high molecular weight polyethylene. An example of such material is commercially known as Dynema.
Though this material has greatly improved low temperature capabilities, it is still not well suited for high temperature applications in challenging environments, such as that required for demanding aerospace applications. To support truly increased temperature capabilities and environmental stability, polymers with enhanced cross-linking and strong pendent groups are desired. The current highest performance polymer materials used in aerospace applications are based on polyimides. These materials have maximum long term continual use temperature capabilities in the range of 550-600 F (288-316 C). These materials, like other organic materials, are challenged in elevated temperature, high humidity environments (hot/wet conditions). Water ingress into the polymers may also result in loss of inter-chain strength and overall degradation of material properties.